I Have 3 Tables with foreign keys to each other.
I want to write a SQL Server Stored Procedure to select records from one of them.
Now, let's suppose that i want all the Winner records referring to the Player records referring to The Game with the ID=2, how can i proceed?
Thank you.
you have specified all the Winner records So that i have used the left join for player and game. But the Overall code works according to the where condition.
Try This,
select w.* from Winner w
left Join Player p on p.ID_player = w.player_FK
left join Game g on g.ID_game = p.Game_FK
where Game.ID_game = 2
You need to use a SELECT and INNER JOIN then to filter on GameID 2 you can use a WHERE clause.
SELECT ID_Winner, Name, Lastname, Player_FK
FROM Winner
INNER JOIN Player on Player.ID_Pplayer = Winner.Player_FK
INNER JOIN Game ON Game.ID_game = Player.Game_FK
WHERE Game.ID_game = 2
Related
I have the following tables:
games:
standings:
I am looking to build a table in the following format for each entry in the games table:
visitor_team_standing | home_team_standing | diff
I have been digging into joins to try and learn but still keep running into a problem.
SELECT
standings.standing visitor_standings,
games.diff
FROM games
INNER JOIN standings ON
games.visitor_team_id = standings.team_id;
However, I can't figure out how to also include the standing for home_team (home_team_id = team-_id).
You just join the standings table twice by giving each one a different alias.
SELECT
visitor.standings visitor_standings,
home.standings home_standings,
games.diff
FROM games
INNER JOIN standings as visitor ON
games.visitor_team_id = visitor.team_id
INNER JOIN standings as home ON
games.home_team_id = home.team_id;
You can try using this code as well.
SELECT
visitor.standings visitor_standings,
home.standings home_standings,
games.diff
FROM games
INNER JOIN standings as visitor
ON
games.visitor_team_id = visitor.team_id
INNER JOIN standings as Home
ON
games.home_team_id = home.team_id;
So I am querying a basketball dataset and I'm using an INNER JOIN statement to get the season stat lines for each Rockets player. However, I am also trying to get a count of how many games they played in the season putting that in a column to get a count of games played for each player.
I'm still learning so I'm trying to experiment and put queries together until I'm stumped. Having trouble with nested queries, thank you in advance.
Pictures:
ER Diagram, Error Message
-- Houston Rockets team_id = 1610612745
-- Jalen Green player_id = 1630224
SELECT player.player_name, player_season.*
FROM player_season
(
SELECT
DISTINCT COUNT (player_id)
FROM player_game_log
AS games_played
)
INNER JOIN
player
ON player_season.player_id = player.player_id
WHERE player_season.team_id = 1610612745
Try adding the subquery directly in the SELECT statement like this:
SELECT player.player_name,
(SELECT DISTINCT COUNT(player_id)
FROM player_game_log
WHERE player_game_log.player_id = player.player_id) AS games_played,
player_season.*
FROM player_season
INNER JOIN player
ON player_season.player_id = player.player_id
WHERE player_season.team_id = 1610612745
Lets say I have three tables with these columns,
Players - id, name
Events - id, name
Games - first_player_id, second_player_id, event_id.
And I need the players details who are playing in a game which is happening in an event.
And I could write query like,
SELECT players.id, events.id as event_id,
(SELECT name as player_one_name from players where id = games.first_player_id),
(SELECT name as player_two_name from players where id = games.second_player_id),
games.id as game_id
FROM events
INNER JOIN games on events.id = games.event_id
INNER JOIN players on games.first_player_id = players.id;"
Here I am using two sub queries to fetch players name. And it gives correct results. Can this query be optimized? For ex, can I remove any subquery or innerjoin ?
FYI, I use PostgreSQL database.
Thanks.
If you do not want sub queries in your select statement then you must provide a join for each subset. Since your database is set oriented the two INNER JOINS would prove more efficient.
SELECT players.id, events.id as event_id,
player_one_name=player_one.name,
player_tow_name=player_two.name
FROM events
INNER JOIN games on events.id = games.event_id
INNER JOIN players player_one on games.first_player_id = player_one.id
INNER JOIN players player_two on games.second_player_id = player_two.id
You must do a join for each foreign key
SELECT players_a.id, events.id as event_id,
players_a.name as player_one_name,
players_b.name as player_two_name,
games.id as game_id
FROM events
INNER JOIN games on events.id = games.event_id
INNER JOIN players players_a on games.first_player_id = players.id
INNER JOIN players players_b on games.first_player_id = players.id
The currently accepted answer is right about joining the players table twice, but mostly wrong otherwise. This would work:
SELECT e.id AS event_id
,g.id AS game.id
,p1.name AS first_player
,p2.name AS second_player
FROM events e
LEFT JOIN games g ON g.event_id = e.id
LEFT JOIN players p1 ON p1.id = g.first_player_id
LEFT JOIN players p2 ON p2.id = g.second_player_id;
Use LEFT [OUTER] JOIN to cover the cases where an event does not have a game or a game does not have both players (yet).
Use table aliases to simplify your syntax. To join the same table twice you also need at least one table alias.
After attaching an alias to a table in the FROM list, only that alias is visible in your query, not the original name of the table.
Study the manual for details.
I'm building a system in which there are the following tables:
Song
Broadcast
Station
Follow
User
A user follows stations, which have songs on them through broadcasts.
I'm building a "feed" of songs for a user based on the stations they follow.
Here's the query:
SELECT DISTINCT ON ("broadcasts"."created_at", "songs"."id") songs.*
FROM "songs"
INNER JOIN "broadcasts" ON "songs"."shared_id" = "broadcasts"."song_id"
INNER JOIN "stations" ON "broadcasts"."station_id" = "stations"."id"
INNER JOIN "follows" ON "stations"."id" = "follows"."station_id"
WHERE "follows"."user_id" = 2
ORDER BY broadcasts.created_at desc
LIMIT 18
Note: shared_id is the same as id.
As you can see I'm getting duplicate results, which I don't want. I found out from a previous question that this was due to selecting distinct on broadcasts.created_at.
My question is: How do I modify this query so it will return only unique songs based on their id but still order by broadcasts.created_at?
Try this solution:
SELECT a.maxcreated, b.*
FROM
(
SELECT bb.song_id, MAX(bb.created_at) AS maxcreated
FROM follows aa
INNER JOIN broadcasts bb ON aa.station_id = bb.station_id
WHERE aa.user_id = 2
GROUP BY bb.song_id
) a
INNER JOIN songs b ON a.song_id = b.id
ORDER BY a.maxcreated DESC
LIMIT 18
The FROM subselect retrieves distinct song_ids that are broadcasted by all stations the user follows; it also gets the latest broadcast date associated with each song. We have to encase this in a subquery because we have to GROUP BY on the columns we're selecting from, and we only want the unique song_id and the maxdate regardless of the station.
We then join that result in the outer query to the songs table to get the song information associated with each unique song_id
You can use Common Table Expressions (CTE) if you want a cleaner query (nested queries make things harder to read)
I would look like this:
WITH a as (
SELECT bb.song_id, MAX(bb.created_at) AS maxcreated
FROM follows aa
INNER JOIN broadcasts bb ON aa.station_id = bb.station_id
INNER JOIN songs cc ON bb.song_id = cc.shared_id
WHERE aa.user_id = 2
GROUP BY bb.song_id
)
SELECT
a.maxcreated,
b.*
FROM a INNER JOIN
songs b ON a.song_id = b.id
ORDER BY
a.maxcreated DESC
LIMIT 18
Using a CTE offers the advantages of improved readability and ease in maintenance of complex queries. The query can be divided into separate, simple, logical building blocks. These simple blocks can then be used to build more complex, interim CTEs until the final result set is generated.
Try by adding GROUP BY Songs.id
I had a very similar query I was doing between listens, tracks and albums and it took me a long while to figure it out (hours).
If you use a GROUP_BY songs.id, you can get it to work by ordering by MAX(broadcasts.created_at) DESC.
Here's what the full SQL looks like:
SELECT songs.* FROM "songs"
INNER JOIN "broadcasts" ON "songs"."shared_id" = "broadcasts"."song_id"
INNER JOIN "stations" ON "broadcasts"."station_id" = "stations"."id"
INNER JOIN "follows" ON "stations"."id" = "follows"."station_id"
WHERE "follows"."user_id" = 2
GROUP BY songs.id
ORDER BY MAX(broadcasts.created_at) desc
LIMIT 18;
Oi
Right to the problem.
SELECT *,t.id AS threadid FROM threads t
LEFT JOIN players p on p.id = t.last_poster
WHERE t.boardid = $boardid
I have two fields in threads called posterid and lastposterid. Which are the IDs of the thread starter / last poster. What I want to do is to get their names from players table.
But how?
You just need to join to your players table twice, like this.
SELECT
threads.*,
starterPlayer.*,
lastPosterPlayer.*
FROM
threads
LEFT OUTER JOIN
players starterPlayer
ON
starterPlayer.id = threads.posterid
LEFT OUTER JOIN
players lastPosterPlayer
ON
lastPosterPlayer.id = threads.lastposterid
You can join to the same table twice and give the table a different alias.
This presumes that there always will be a first and last poster, if this is the case then you want an INNER JOIN rather than a LEFT JOIN, you will need to change the select statement to get the relevant fields.
SELECT t.id AS threadid, playerFirst.name AS FirstPoster, playerLast.name as LastPoster
FROM threads t
INNER JOIN
players playerFirst ON playerFirst.id = t.posterid
INNER JOIN
players playerLast ON playerLast.id = t.lastposterid
How about...
SELECT *,
(SELECT name
FROM players
WHERE players.id = threads.posterid) AS poster,
(SELECT name
FROM players
WHERE players.id = threads.lastposterid) AS last_poster
FROM threads;